It might be to do with where the pattern is imported from - if USA or Canada, it will still be imperial. Kinda ironic considering the pains the US went to not to be under the Empire...
I work out everything in Imperial then convert it into metric before I buy it, because that's what most of the shops want.
Went into a shop the the other day armed with my metric shopping list, only to be asked 'What's that in feet and inches then?'
Some Imperial sizes still remain in lots of areas, although they often are quoted in metric.